Firefox developer tools adding a new rule?

Question

I decided to try out the built in Firefox Developer Tools. Seems to be nice, but...

I can\'t find out how to add a new rule to the CSS from Inspector/Rules. By that

Answer 1

As of Firefox 33 (in nightly right now https://nightly.mozilla.org/), this works.

When you have a node selected in the inspector, you can click on any of the selectors in the "Rules" sidebar to edit them.